LED CURRENT CONTROL

摘要

An LED control circuit for controlling a current supplied to an LED unit is disclosed. A sense resistor is included for sensing an output current provided from an output node. A comparator circuit is provided for detecting upper and lower thresholds in the output current based on the voltages at ends of the sense resistor, and for controlling a current supply to maintain the current between the thresholds. The comparator circuit comprises a reference current source and reference resistors, for generating upper and lower threshold references. The comparator circuit further comprises a comparator for detecting a mid-range voltage dependent on the output current and deriving a control signal which indicates if the detected voltage is above or below the mid-range voltage. The control signal is used to adjust the reference current source, thereby to vary the upper and lower threshold references to maintain a constant median or average output current.

主权项

1. An LED control circuit for controlling a current supplied to an LED unit, the control circuit comprising:
a sense resistor for sensing an output current provided from an output node; and a comparator circuit for detecting upper and lower thresholds in the output current based on the voltages at each end of the sense resistor, and for controlling a current supply to maintain the current between the thresholds, wherein the comparator circuit comprises a reference current source and reference resistors, for generating upper and lower threshold references, wherein the comparator circuit further comprises a comparator for detecting a mid-range voltage dependent on the output current and deriving a control signal which indicates if the detected voltage is above or below the mid-range voltage, and wherein the control signal is used to adjust the reference current source, thereby to vary the upper and lower threshold references to maintain a constant median or average output current.